INSECTS

The Great Plains of North America, like every
other terrestrial ecosystem, has always depended
upon insects for its existence. Insects
are essential for maintaining plant life on the
Plains through movement of nutrients, improving
soil, accelerating organic decay, and
pollinating plants. Additionally, insects form
the foundation of the animal food web, upon
which many species depend. As Plains ecosystems
have given way to agroecosystems, the
importance of insects has been altered, yet it
still remains.

Insects are, by far, the most diverse animals
on earth, and this is as true of the Plains as it is
of the tropics. More than 100,000 insect species
are known to exist in North America, and
of these at least tens of thousands occur in the
Great Plains. Although most insect groups are
represented on the Plains, probably the most
common are the insect orders Orthoptera
(grasshoppers and crickets), Hemiptera (true
bugs, various insects with sucking mouthparts),
Diptera (true flies), Coleoptera (beetles),
Lepidoptera (butterflies and moths),
and Hymenoptera (ants, bees, and wasps).

The intimate association of insects and
plants is essential for maintaining prairies. Soil
structure and nutrient flow depend largely on
the action of ants in moving material from the
soil surface to plant root zones. A complex of
dung beetle (scarab) species is essential for the
rapid decomposition of animal dung, originally
from herds of bison and now from herds
of cattle. Similarly, other species of beetles and
flies are crucial in recycling dead animal tissue.
Finally, many prairie plants depend on insect
pollinators, especially various species of native
bees. Certainly not all associations of insects in
the Great Plains have been beneficial or benign.
Periodic grasshopper plagues removed
so much vegetation that many larger herbivores,
like bison, subsequently starved. Also
biting flies and various internal and external
insect parasites tormented animals, including
humans. The plants of the Plains, however,
cannot exist without their associated insects.

As some plant species have diminished or
disappeared, so too have their associated insects.
This is especially true for many prairie butterflies,
which have a limited range of host
plants. The reduction of the prairie has also led
to the decline of other Plains animals and, therefore,
of the insects which depend upon them.
The American burying beetle (Nicophorus
americus), an endangered insect species once
found in all of eastern North America, now
only occurs in scattered populations in the
Great Plains (plus one remnant population in
Rhode Island). Whether or not the decline of
this species is associated with the decline of
specific host carrion or other changes in habitat
is unclear. Sometimes, as with prairie butterflies
and moths, the loss of plant species can
be clearly associated with loss of their associated
insects. In other instances, the relationships
are more problematic. One of the most
striking mysteries involves the disappearance
of the Rocky Mountain locust (Melanoplus
spretus Walsh) that swept across the Great
Plains in massive swarms of billions through
the 1870s but apparently became extinct by the
early 1900s. It seems likely that changes in habitat,
possibly through agriculture and loss of
egg-laying sites, explain the extinction of this
grasshopper.

Continuing threats to insect biodiversity of
the Plains also are associated with habitat
change and loss. The management of existing
prairies is of key importance in maintaining
biodiversity. In particular fire and its negative
impact on invertebrate communities has become
a serious issue in managing remnant
prairies. Similarly identifying and protecting
other unique Plains habitats is another compelling
issue for maintaining insect biodiversity.
For example, one of the most endangered
insects in the United States, the Salt Creek tiger
beetle (Cicindela nevadica lincolniana), is a
member of a complex of tiger beetle species
that occur exclusively in salt marshes of the
Eastern Great Plains. The decline of these insects
directly follows from the destruction of
salt marsh habitats through agriculture and
urbanization.

Human use of the Great Plains has profoundly influenced the insect fauna, probably
in ways we can never completely recognize
(given that the Plains was substantially changed
before its insect fauna was thoroughly studied).
The destruction of the great bison herds
and the ecosystems of which they were a part
undoubtedly altered insect diversity and abundance.
In general, urbanization and agriculture
have reduced insect biodiversity. Agroecosystems
are simplified as compared to natural
ecosystems. This simplification leads to reduced
species diversity, but may also result in
large population increases of individual species,
such as the corn rootworm beetles. Agriculture
and urbanization also introduced
many nonnative insects to the Great Plains,
principally domestic species and pest species
associated with crop plants, and this is a continuing
process.

The introduction of nonnative plants such
as crops not only leads to the introduction of
new insects but also to the adaptation of native
insects to these new crops. For example,
with the introduction of soybean in the 1930s
and 1940s, a native beetle, Cerotoma trifurcata
(bean leaf beetle), rapidly moved from native
leguminous hosts to become a soybean pest. A
more striking example of this adaptation is
the beetle Leptinotarsa decemlineata switching
hosts from one solanaceous plant, buffalo bur,
to another, potato. This insect, now known as
the Colorado potato beetle, is one of the most
severe potato pests throughout the world (and
holds the dubious distinction of being one of
the insect species most resistant to insecticides).
It diffused from the Central Great
Plains in the 1870s to most potato-growing
regions of the world in less than a century,
highlighting the influence of trade and human
commerce on insect distributions.

Human interactions with insects largely
have been confrontational rather than appreciative.
One exception is that many Native
peoples of the Great Plains recognized the importance
of insects as an essential feature of
nature and speak to the importance of insects
in their oral traditions. Some Native people
also ate insects, such as grasshoppers and
crickets, as an occasional feature of their diet.
For European American settlers of the Plains,
insects were either ignored or viewed as pests.
Black flies and mosquitoes were constant irritants,
and insect-borne diseases like malaria
and yellow fever were widespread in at least
the Eastern Great Plains in the 1800s. Although
these diseases no longer occur in the
Great Plains, various encephalitis viruses,
transmitted by mosquitoes, and Lyme disease,
transmitted by ticks, still do present human
health risks. Insects, especially through outbreaks
of grasshoppers, crickets, and armyworms,
also were a serious impediment to
crop production as European American agriculture
moved onto the Great Plains. Insects
are still a significant factor in agriculture on
the Plains, not only through exceptional pest
outbreaks, but also through the routine occurrence
of many pest species.

The future of insect biodiversity on the
Plains is inexorably tied to the conservation
of their habitats. The legacy of western attitudes
toward insects, reinforced by potential
health and agricultural risks from insects, is
that insects are mostly ignored or despised.
However, insects are an essential element of
the Great Plains. Their fate, for good or ill,
will mirror that of the Great Plains ecosystem
itself.